Tennis world erupts over Genie Bouchard's appearance in Nick Kyrgios' box

Tennis fans are in a collective frenzy after Eugenie Bouchard sat in Nick Kyrgios’ players box at Wimbledon on Thursday.

There were hoards of keen observers for Kyrgios’ grudge match with Rafael Nadal on centre court at the All England Club.

And Bouchard was one of them.

Sitting right behind Kyrgios’ father and entourage was none other than the Canadian tennis star and her sister.

Fans were immediately intrigued about why she was there in Kyrgios’ corner, and even more so when she sent out a tweet of the Aussie serving with a number of love heart eyes emojis.

She even hit back at a number of fans who criticised Kyrgios for serving underarm.

Could Kyrgios and Bouchard be an item?

Kyrgios and Bouchard have previously played mixed doubles together and seem to get along well off the court.

The pair practiced together in the lead-up to Wimbledon.

“He’s so chill, he’s very nice and was making the practice for me, which I appreciated,” Bouchard said.

“I asked him to do a couple really hard serves. I was able to return a few.

“It’s great for reaction because the ball comes so much faster — a different spin, more aggressive spin.

“Usually after hitting with a guy like that the ball seems slower when I’m hitting with a girl.”

Fans were certainly open to the possibility.

Fans treated to Wimbledon classic

An audacious under-arm ace and the second-fastest serve in tennis history weren’t enough to spare Kyrgios from a drama-charged loss.

In a gripping encounter that exceeded all the hype, Nadal avenged his stunning defeat to Kyrgios on the sport's most hallowed court five years ago with a pulsating four-set triumph on Thursday.

Living up to its grudge-match-of-the year status, Nadal resisted the volatile Australian's spirited challenge with a 6-3 3-6 7-6 (7-5) 7-6 (7-3) victory in a three-hour-and-three-minute classic.

A series of verbal jousts between the two, chiefly Kyrgios's taunting of the "super salty" Spaniard and Nadal's "idiot" Uncle Toni in an explosive podcast, had dominated the build-up.

But such tasty barbs served as merely the appetiser to a spicy main course that had Wimbledon's centre court crowd - and the umpire - on the edge of their seats.

Raging after losing a challenge on his first serve in the eighth game, Kyrgios promptly smashed down an unstoppable, untouchable second serve clocked at 143mph (230kph).

Only Ivo Karlovic's 144mph (232kph) effort at the 2007 Legg Mason Classic has ever topped Kyrgios's rocket serve, according to ATP statistics.

The sport's most unpredictable talent quickly followed up with his under-arm ace, which brought a smile from even the fiercely intense Nadal.

Wimbledon's famously conservative fans had never seen anything like it, and the daring tactic appeared to briefly unsettle Nadal.

with AAP